The present invention relates to frame rate conversion.
For a digital video system, the video is encoded and decoded using a series of video frames. Frames of a video are captured or otherwise provided at a first frame rate, typically a relatively low frame rate (e.g., 24 Hz or 30 Hz). A video presentation device often supports presenting the video at a second frame rate, typically a relatively high frame rate (e.g., 60 Hz or 120 Hz). With the difference in the frame rates, the video frame rate is modified from the first frame rate to the second frame rate using a frame rate up conversion process. Frame rate conversion may be used to match the frame rate of the video to the display refresh rate which tends to reduce video artifacts, such as motion judder. In addition, frame rate conversion also tends to reduce motion blur on liquid crystal displays due to the hold-type nature of liquid crystal displays.
Frame rate up conversion techniques may create interpolated frames using received frames as references or may create new frames using frame repetition. The new video frames that are generated may be in addition to or in place of the frames of the input video, where the new frames may be rendered at time instances the same as and/or different from the time instances that the input frames are rendered. The frame interpolation may be based upon using a variety of different techniques, such as using a frame interpolation technique based on motion vectors of the received frames, such that moving objects within the interpolated frame may be correctly positioned. Typically, the motion compensation is carried out on a block by block basis. While the motion compensated frame rate up conversion process provides some benefits, it also tends to be computationally expensive. Conventional block-by-block motion vector estimation methods do not consider which aspects of the moving image are salient and relevant to achieving high image quality frame interpolation.
Accordingly, there is a need to determine motion based effects for frame rate conversion that is based upon a sufficiently accurate measure of the motion at a significantly reduced computational cost, without the need to determine highly accurate motion vectors. It is also desirable to describe the motion between frames with a reduced number of parameters, in order to reduce computational cost. It is also desirable to retain a sufficiently accurate rendition of the motion between frames so as to achieve high quality frame interpolation.
The foregoing and other objectives, features, and advantages of the invention may be more readily understood upon consideration of the following detailed description of the invention, taken in conjunction with the accompanying drawings.